Stuff to take on an extended ride: (my list is not all-inclusive, just off the top of my head)
2 pairs bike shorts
2 bike shirts
1 pair zip-off-leg pants
1 off-bike t-shirt that can double as sleep-shirt
Light weight rain jacket.
Warm jacket. Fleece is bulky but soft enough to double as a pillow when camping.
2 pr bike socks
All clothes should be light-weight and able to be washed in gas station sink and dry fast on the back of the bike. You might also be washing clothes in hot water in a middle of nowhere laundromat. Nothing non-colorfast or ruined by bike grease or crusted salt-sweat lines.
Bike sandals with clips, which can double as in-town shoes. Keen & Teva make them.
Waterproof panniers if you can afford them. I had to pack my clothes in 2 gallon ziplocs and sit on the bags every morning to get the air out before zipping them closed.
Small bottle Dawn dish soap for washing water bottles and bike shorts.
Sample size shampoo, soap, razor. You also pick these up at motels as you go.
Sleeping bag for the mountains
Sleep sack of thin flat sheet sewn up the side and bottom for hot weather. I bought one with gaudy orange flowers in the original package at a thrift store in North Dakota. It was made in USA, so you know how old that one is.
Tent with reliable mosquito netting.
Thermarest or lightweight mattress for camping. There's a reason they call it the ROCKY Mountains. Makes for a tough nights sleep without a mattress.
Mosquito repellant, OFF Deep Woods
Sunscreen, SPF 80
Waterproof drybags for sleeping bags and Thermarests.
Thick plastic spoon. The ones from Wendy's are like iron.
Minimal maps. You can pick up free state maps and state bike route maps along the way.
Diaper cream for sore fannies and sunburned noses.
Band aids. Coban (tan non-stick vet wrap stuff)
Small tube Neosporin
Ibuprofen or Alleve tablets
Pepto Bismol tabs or Immodium. They get crushed to powder in the panniers, but still useful.
Deodorant. Didn't bring it at first, but our children informed us that it is an essential parent personal care item.
Vitamins with iron if travelling with children. Most fast food is maximum grease, minimal fruits, vegetables and sources of iron.
What not to bring:
Books. You can buy them for .25 at the library cast-off cart and donate them a few days later. I was really too tired to read anyway. When I had free-time I talked to people at the campgrounds.
Nice clothes. You won't be going anyplace nice in goofy bike shoes and bike hair.
Underwear. Superfluous in most cases. Our 10 year-old son refers to this secret freedom as "going commando."
Cooking gear. You can survive from grocery stores and little cafes if you're not a picky eater. Dairy Queen has great cereal bowls if you reuse their small salad bowl and top.
Flashlights. Arguable. A small headlamp that can be hung from the top-loop in the tent is handy for looking at maps at night.
Lots of cash or travelers cheques. Even the little gas stations have ATM's now.
Rain pants. Usually I just ride in bike shorts and rain jacket unless cold weather. Caveat: I HATE raingear.
Rain booties: debatable among our family members. If you only have one pair of bike shoes and they get soaked, they take 2-3 days to dry if you are camping.
Warm gloves. I rode with poly-pro liner gloves with or without waterproof over-gloves. In Oregon Cascade Mtns in April, really needed warm gloves, wind-resistant, but not since then.
Bike computer. A point of controversy in our family. My husband has one. I don't. The kids pester him to know what the current speed and distance are. They don't bug me with the same questions. I watch the mile marker signs. Unless you are off-road, highways are well-marked in the USA.